With increasing development of photographing technologies, portable electronic devices such as mobile phones or tablet computers are usually equipped with image pickup devices for capturing images. Moreover, most of the modern image pickup devices have focusing functions. By the focusing function, the object at different distances from the image pickup device can be clearly imaged into the image pickup device. In particular, by adjusting a position of a camera module 9 (see FIG. 1) of the image pickup device, the ambient light beam can be introduced into the image pickup device and accurately focused on a sensing element of the image pickup device. Consequently, the captured image can be clearly shown. Obviously, an actuator 1 (see FIG. 1) for driving the camera module 9 to perform a focusing operation is one important factor that influences the imaging quality.
FIG. 1 schematically illustrates a conventional actuator and a camera module to be driven by the actuator. The actuator and the camera module are disclosed in for example U.S. Pat. No. 8,049,971. As shown in FIG. 1, the actuator 1 comprises a piezoelectric driving unit 11, a carrier part 12, a base 13, and plural balls 14. The carrier part 12 is disposed within the base 13 for supporting the camera module 9. The piezoelectric driving unit 11 is contacted with a first side of the carrier part 12. The piezoelectric driving unit 11 is used for moving the carrier part 12 upwardly or downwardly in order to achieve the focusing function. The plural balls 14 are located at a second side of the carrier part 12, and clamped between the carrier part 12 and the base 13. When the carrier part 12 is moved by the piezoelectric driving unit 11, the plural balls 14 are rolled along an inner wall of the base 13. Consequently, the carrier part 12 is moved in a direction parallel with an optical axis 91 of the camera module 9. In such way, the carrier part 12 will not be aslant moved (e.g. in the direction indicated as the dotted line L of FIG. 1).
However, since one side of the carrier part 12 is supported by the piezoelectric driving unit 11 in a single-point contacting manner only, the stability of moving the carrier part 12 is not satisfied. Moreover, during the assembling process, the balls 14 and the carrier part 12 are respectively installed in the base 13. For fixing the balls 15 between the carrier part 12 and the base 13, the actuator 1 should be equipped with an additional component for fixing the balls 14. Under this circumstance, the complexity of the assembling process is increased.
From the above discussions, the conventional actuator 1 for driving the camera module 9 needs to be further improved.